[Kinetic characteristics of the action of tocopherols as antioxidants]

Ability of tocoferols to react with free radicals (constant K7) is determined by means of chemoluminescent method. A succession of activities is obtained for tocoferol homologues; this succession coincides with that of their biological activity. The products of oxidative transformations of tocoferols are shown to posess an inhibiting activity. Formation of sufficiently active free radicals is a characteristic feature of the antioxidative action of tocoferols. The extremal dependence of the antioxidative activity of tocoferols on their concentration is explained by the participation of these radicals in the reactions of the continuation of the oxidation chain. According to their kinetic characteristics tocoferols fall into the category of weak antioxidants. Peculiarities of the antioxidative effect of tocoferols help to explain their high biological activity. Since tocoferols have high enough values of the constants K7, even slight changes in their concentration in lipids will essentially affect the rate of oxidative processes. This peculiarity makes them rather unique, since they are first spent in the oxidation reactions proceeding in lipids, and they can be substituted only by the substances which have the constants K7 of the same order. The specificity of antioxidative properties of tocoferols enables their efficient control over peroxide oxidation of lipids.